The present invention relates generally to flux sources or permanent magnet structures wherein magnetically rigid (hereinafter MR) materials are utilized to derive high magnitude magnetic fields of uniform flux density in enclosed cavities and more particularly, to such flux sources with annular cavities.
In the electronic arts, magnetic fields are employed in various applications to control the dynamics of charged particles. One such application is electron beam focusing wherein the repelling forces between the beam's electrons is overcome with magnetic fields directed perpendicularly to the path travelled by the beam which is thereby precluded from spreading out. Another such application is found in radiation sources wherein magnetic fields are applied across the path travelled by charged particles to accelerate those particles thereacross in a perpendicular direction. Furthermore, very large magnetic fields are employed in NMR (Nuclear Magnetic Resonance) imagers which have become a very important tool in medical diagnostics.
Because of the massive solenoids and bulky power supplies which are associated therewith, electromagnets present problems in most applications where they are employed to derive magnetic fields. However, before MR material was used for permanent magnet structures, electromagnets were the generally accepted design approach for deriving magnetic field magnitudes of any significance. Such was particularly true when a magnetic field confined within a work space or cavity was desired. This was so because suitable permanent magnet structures require exterior cladding magnets to confine the magnetic field, as well as bucking magnets and pole pieces to preclude flux leakage to the exterior of the structures and conventional magnets do not have sufficient coercivity to serve in these capacities.